For many people, sweating occurs due to eating hot and spicy food. For others, however, it happens frequently after eating any food.
In these cases where eating any food causes sweating, it is most likely due to nerve damage in or around the parotid gland, the gland in the cheek that produces saliva. When this occurs, it tends to happen on one side of the face and is known as Frey's syndrome.
In some rare cases, people with diabetes mellitus may experience bilateral gustatory sweating, with sweating on both sides of the face.
In this article, we compare gustatory sweating with regular sweating and look at what can be done to treat or prevent cases of gustatory sweating.
Regular sweating after eating vs. Frey's syndrome
Sweating on the face, neck, or scalp during or after eating is relatively common.
Gustatory sweating is similar to Frey's syndrome, and the two terms are often used interchangeably.
It is not uncommon for people to sweat during or after eating. For most people, sweating occurs on the face, scalp, or neck when they are eating spicy or hot foods and drinks.
In these cases, the person's body is responding naturally to stimulation of a rise in body temperature through sweat. This is a normal reaction and not a cause for concern.
A person with Frey's syndrome has a problem with their parotid gland and may start to sweat and flush on the scalp, face, ears, and neck after eating any food. However, foods that make people produce a lot of saliva are most likely to trigger the reaction.
Typically, a person develops Frey's syndrome as a result of surgery near the parotid gland. However, other people may experience Frey's syndrome due to another injury or illness that affects the parotid gland.
In an attempt to heal themselves, damaged nerves sometimes get mixed up with other nerves, causing a person to produce sweat instead of saliva.
Typically, Frey's syndrome occurs on just one side of the face. Although both cheeks have a parotid gland, only one may have been damaged.
Gustatory sweating can occur for no apparent reason or as a result of an underlying condition, such as diabetes or Parkinson's disease. These diseases can also cause damage to the nerves in the mouth. When the nerves become injured, they can become confused and cause sweating.
Unlike Frey's syndrome, other types of gustatory sweating often occur on both sides of the face. Unlike regular sweating due to eating spicy or hot foods, gustatory sweating causes a person to sweat and flush after eating, thinking, or even talking about food.
This sweating and flushing may occur around the temples, cheeks, neck, forehead, chest, or lips.
Gustatory sweating may cause some people distress, as thinking about food can trigger the reactions of sweating. Since there is often an underlying cause, a person should talk to their doctor to find out what may be causing the sweating.
Causes and associated conditions
Eating food may cause gustatory sweating. In some cases, simply talking or thinking about food may cause it.
Gustatory sweating is triggered by the following:
- eating food
- thinking about food
- talking about food
Frey's syndrome is triggered by eating food, but it can also occur even while thinking or talking about food. It develops on one side of the face in the area of the affected parotid gland.
Gustatory sweating is often the result of an underlying condition. Some of the more common conditions that may cause gustatory sweating include:
- diabetes melliltus
- a viral infection affecting the face, such as Bell's palsy or shingles
- injury to the face
When to see a doctor
People do not necessarily need to see a doctor after sweating from eating food. Those who only sweat while eating either very hot or spicy foods have no reason to be concerned.
Some people who experience Frey's syndrome may consider it to be a nuisance but do not consider it significant enough to seek help.
However, those people who sweat profusely after tasting, smelling, or talking about food may wish to see a doctor. A doctor can diagnose Frey's syndrome or another type of gustatory sweating by:
- noting the characteristic symptoms
- taking a medical history
- carrying out the minor iodine-starch test
The minor iodine-starch test involves swabbing the area of the body where the sweating occurs with an iodine solution. The doctor will then apply a starch, such as corn starch, over the iodine.
When the starch and iodine are in place, the doctor will stimulate the mouth, often with an acidic food. A person with Frey's syndrome or other gustatory sweating will show a discoloration where the sweat forms.
Once diagnosed, a doctor can help a person identify the underlying cause. In some cases, it may be due to surgery or another known condition that the person has. In others, the doctor may wish to carry out further testing to find out what might be causing the problem.
Knowing the cause helps the doctor know how to treat the sweating.
Treatment and prevention
Botox may be used to treat Frey's syndrome.
Treatment for gustatory sweating depends on what is causing it.
A doctor treating Frey's syndrome typically focuses on the symptoms. There is often little that can be done to fix the damaged nerves. Surgical procedures are available to replace affected skin, but they are risky and not often advised.
A doctor may prescribe medicines and topical creams that help block undesired activities of the nervous system, such as sweating.
One medication that has proved quite successful to treat sweating associated with Frey's syndrome, however, is botulinum toxin type A (Botox). The medication is injected into the affected area to stop the sweating, and there are minimal side effects.
One disadvantage of botulinum toxin is that the effects are temporary. Research shows that people tend to need repeat injections after 9–12 months. The United States Food and Drug Administration (FDA) do not currently approve the use of Botox for treating gustatory sweating, however.
Treating gustatory sweating when it is not the result of injury or surgery often requires treating the underlying disease or disorder if it is known.
People who suspect that their gustatory sweating is a result of an underlying condition should speak to their doctor about any other symptoms they experience.
Gustatory sweating is considered to be a harmless condition. Some people find that they can deal with the symptoms with no need for medical intervention.
Where the sweating is profuse and a cause for embarrassment, people may want to treat their symptoms.
It is also important that people seek medical attention if profuse sweating is unexplainable, as it could indicate an underlying condition.